connecting IC with external components

i want to understand the thought process and ideas behind these:



1 - what is the n-FET and diode (Q1 and Q2) component means?

2 - why the 4.7kOhm resistors used instead of 10kOhm like in the datasheet here (also applicable to other circuit,this is just an example to help me understand)
https://www.pololu.com/file/download/LSM303DLHC.pdf?file_id=0J564

3 - how designers verify that the component values used will yield the desired result? i mean they are only provided with IC and its datasheet,sure they need to do simulations to verify the circuit.
do they model the IC?How's the simulation done for e.g?

4 - any tut/books to help me understand better how to connect IC with external components?like from a pin of an IC with sensor/op-amp,choose values,what to consider, how to verify etc.
or IC pin as a driver.

thx

1 - what is the n-FET and diode (Q1 and Q2) component means?

Click to expand...

n-FET means N type field effect transistor,Q1,Q2 are symbol of a n-FET

3 - how designers verify that the component values used will yield the desired result? i mean they are only provided with IC and its datasheet,sure they need to do simulations to verify the circuit.

Click to expand...

Users get the logical of the device and the company who yield the circuit have the internal circuit of it.